And, if we agree to use the term in this sense, then it is obvious that no more can be necessary for the truth of the assertion that there are material things, than is necessary for the truth of judgments of the kind with which I propose to deal. But no more can be necessary for the truth of these judgments than is actually asserted in or logically implied by them. And if we approach the question what is necessary for the truth of the assertion that there are material things, by asking what it is that we actually assert when we make such judgments as these, certain reasons for doubting how much is necessary are, I think, brought out much more clearly, than if we approach the question in any other way. Many philosophers have told us a very great deal as to what they suppose to be involved in the existence of material things; and some, at least, among them seem to have meant by "material things" such things as inkstands, fingers and clouds. But I can think of only one type of view as to the constitution of material things, which is such that it is tolerably clear what answer those who hold it would give to the simple question; What is it that I am judging, when I judge, as I now do, that that is an inkstand? The type of view I mean is that to which the view that Mill suggests, when he explains what he means by saying that Matter is a Permanent Possibility of Sensation, and also the view or views which Mr. Russell seems to suggest in his "Our Knowledge of the External World," seem to belong. In the case of views of this kind, it is, I think, tolerably clear what answer those who hold them would give to all the questions I want to raise about judgments of the kind I have described. But it does not seem to me at all certain that any view of this type is true; and certainly many philosophers have held and do hold that all views of this type are false. But in the case of those who do hold them to be false, I do not know, in any single case, what answer would be given to all the questions which I want to raise. In the case of philosophers, who do not accept any view of the Mill-Russell type, none, so far as I know, has made it clear what answer he would give to all my questions: some have made it clear what answer they would give to some of them; but many, I think, have not even made it clear what answer they would give to any. Perhaps there is some simple and satisfactory answer, which has escaped me, that such philosophers could give to all my questions; but I cannot help thinking that assumptions as to the nature of material things have too often been made, without its even occurring to those who made them to ask, what, if they were true, we could be judging when we make such judgments as these; and that, if this question had been asked, it would have become evident that those assumptions were far less certain than they appeared to be.
I do not know that there is any excuse whatever for calling all judgments of the kind I mean "judgments of perception." All of them are, of course, judgments about things which we are at the moment perceiving, since, by definition, they are judgments about things which we are seeing or feeling with our hands; and all of them are, no doubt, also based upon something which we perceive about the thing in question. But the mere fact that a judgment is both about a thing which I am perceiving, and also based upon something which I perceive about that thing, does not seem to be a sufficient reason for calling it a judgment of perception; and I do not know that there is any other reason than this for calling all judgments of the kind I mean judgments of perception. I do not want therefore, to assert that all of them are so. But it seems to me quite plain that enormous numbers of them are so, in a perfectly legitimate sense. This judgment, which I now make, to the effect that that is a door, seems to me quite plainly to be a judgment of perception, in the simple sense that I make it because I do, in fact, see that that is a door, and assert in it no more than what I see; and what I see I, of course, perceive. In every case in which I judge, with regard to something which I am seeing or feeling with my hands, that it is a so-and-so, simply because I do perceive, by sight or touch, that it is in fact a thing of that kind, we can, I think, fairly say that the judgment in question is a judgment of perception. And enormous numbers of judgments of the kind I mean are, quite plainly, judgments of perception in this sense. They are not all, for the simple reason that some of them are mistaken. I may, for instance, judge, with regard to an animal which I see at a distance, that it is a sheep, when in fact it is a pig. And here my judgment is certainly not due to the fact that I see it to be a sheep; since I cannot possibly see a thing to be a sheep, unless it is one. It, therefore, is not a judgment of perception in this sense. And moreover, even where such a judgment is true, it may not always be a judgment of perception, for the reason that, whereas I only see the thing in question, the kind of thing which I judge it to be is of such a nature, that it is impossible for any one, by sight alone, to perceive anything to be of that kind. How to draw the line between judgments of this kind, which are judgments of perception, and those which are not, I do not know. That is to say, I do not know what conditions must be fulfilled in order that I may be truly said to be perceiving, by sight or touch, such things as that that is a door, this is a finger, and not merely inferring them. Some people may no doubt think that it is very unphilosophical in me to say that we ever can perceive such things as these. But it seems to me that we do, in ordinary life, constantly talk of seeing such things, and that, when we do so, we are neither using language incorrectly, nor making any mistake about the facts—supposing something to occur which never does in fact occur. The truth seems to me to be that we are using the term "perceive" in a way which is both perfectly correct and expresses a kind of thing which constantly does occur, only that some philosophers have not recognised that this is a correct usage of the term and have not been able to define it. I am not, therefore, afraid to say that I do now perceive that that is a door, and that that is a finger. Only, of course, when I say that I do, I do not mean to assert that part of what I "perceive," when I "perceive" these things, may not be something which, in an important sense, is known to me only by inference. It would be very rash to assert that "perception," in this sense of the word, entirely excludes inference. All that seems to me certain is that there is an important and useful sense of the word "perception," which is such that the amount and kind of inference, if inference there be, which is involved in my present perception that that is a door, is no bar to the truth of the assertion that I do perceive that it is one. Vast numbers, then, of the kind of judgments with which I propose to deal seem to me to be, in an important and legitimate sense, judgments of perception; although I am not prepared to define, any further than I have done, what that sense is. And though it is true that the questions which I shall raise apply just as much to those of them which are not judgments of perception as to those which are, it is, of course, also true that they apply just as much to those which are as to those which are not; so that I shall be really dealing with a large and important class among judgments of perception.
It is true that, if certain views which, if I understand them rightly, some Philosophers have seriously entertained, were true ones, it would be quite impossible that any of them should be judgments of perception. For some philosophers seem to me to have denied that we ever do in fact know such things as these, and others not only that we ever know them but also that they are ever true. And, if, in fact, I never do know such a thing, or if it is never true, it will of course, follow that I never perceive such a thing; since I certainly cannot, in this sense, perceive anything whatever, unless I both know it and it is true. But it seems to me a sufficient refutation of such views as these, simply to point to cases in which we do know such things. This, after all, you know, really is a finger: there is no doubt about it: I know it, and you all know it. And I think we may safely challenge any philosopher to bring forward any argument in favour either of the proposition that we do not know it, or of the proposition that it is not true, which does not at some point, rest upon some premiss which is, beyond comparison, less certain than is the proposition which it is designed to attack. The questions whether we do ever know such things as these, and whether there are any material things, seem to me, therefore, to be questions which there is no need to take seriously: they are questions which it is quite easy to answer, with certainty, in the affirmative. What does, I think, need to be taken seriously, and what is really dubious, is not the question, whether this is a finger, or whether I know that it is, but the question what, in certain respects, I am knowing, when I know that it is. And this is the question to which I will now address myself.
To begin with there is one thing which seems to me to be very certain indeed about such judgments. It is unfortunately a thing which I do not know how properly to express. There seem to me to be objections to every way of expressing it which I can think of. But I hope I may be able to make my meaning clear, in spite of the inadequacy of my expression. The thing I mean is a thing which may to some people seem so obvious as to be scarcely worth saying. But I cannot help thinking that it is not always clearly recognised, and even that some philosophers, to judge from what they say, might perhaps dispute it. It seems to me to be an assumption which is silently made in many treatments of the subject, and, as I say, it seems to me to be very certain indeed. But I think it is at all events worth while to try to make the assumption explicit, in case it should be disputed. If it really is not true, then the other questions to which I shall go on, and which seem to me really dubious and difficult, do not, I think, arise at all.
I will try to express this fundamental assumption, which seems to me so very certain, by saying it is the assumption that, in all cases in which I make a judgment of this sort, I have no difficulty whatever in picking out a thing, which is, quite plainly, in a sense in which nothing else is, the thing about which I am making my judgment; and that yet, though this thing is the thing about which I am judging, I am, quite certainly, not, in general, judging with regard to it, that it is a thing of that kind for which the term, which seems to express the predicate of my judgment, is a name. Thus, when I judge, as now, that That is an inkstand, I have no difficulty whatever in picking out, from what, if you like, you can call my total field of presentation at the moment, an object, which is undoubtedly, in a sense in which nothing else is, the object about which I am making this judgment; and yet it seems to me quite certain that of this object I am not judging that it is a whole inkstand. And similarly when I judge, with regard to something which I am feeling in my pocket, "This is a coin," I have no difficulty in picking out, from my field of presentation, an object, which is undoubtedly the object with which my judgment is concerned; and yet I am certainly not judging with regard to this object that it is a whole coin. I say that alwayst when I make such a judgment, I can pick out the one, among the objects presented to me at the time, about which I am making it; but I have only said that in general I am not judging with regard to this object that it is a thing of the kind, for which the term, which seems to express the predicate of my judgment, is a name. And I have limited my second proposition in this way, because there are cases, in which it does not, at first sight, seem quite so certain that I am not doing this, as in the two instances I have just given. When, for instance, I judge with regard to something, which I am seeing, "This is a soap-bubble," or "This is a drop of water," or even when I judge "This is a spot of ink," it may not seem quite so plain, that I may not be judging, with regard to the very object presented to me, that it is, itself, a whole soap-bubble, a whole drop of water, or a whole spot of ink, as it always is, in the case of an inkstand, or a coin, that I never take the presented object, about which I am judging, to be a whole inkstand, or a whole coin. The sort of reason why I say this will, of course, be obvious to any one, and it is obviously of a childish order. But I cannot say that it seems to me quite obvious that in such a case I am not judging of the presented object that it is a whole drop of water, in the way in which it does seem to be obvious that I am not judging of this presented object that it is an inkstand. That is why I limit myself to saying that, in general, when I judge "That is a so-and-so" I am not judging with regard to the presented object, about which my judgment is that it is a thing of the kind in question. As much as this seems to me to be a thing which any child can see. Nobody will suppose, for a moment, that when he judges such things as "This is a sofa," or "This is a tree," he is judging, with regard to the presented object about which his judgment plainly is, that it is a whole sofa or a whole tree: he can, at most, suppose that he is judging it to be a part of the surface of a sofa or a part of the surface of a tree. And certainly in the case of most judgments of this kind which we make, whether in the case of all or not, this is plainly the case: we are not judging, with regard to the presented object about which our judgment plainly is, that it is a thing of the kind, for which the term which appears to express the predicate of our judgment, is a name. And that this should be true of most judgments of this kind, whether of all or not, is quite sufficient for my purpose.
This much, then, seems to me to be very certain indeed. But I will try to make clearer exactly what I mean by it, by mentioning a ground on which I imagine it might perhaps be disputed.
The object of which I have spoken as the object, about which, in each particular case, such a judgment as this always is a judgment, is, of course, always an object of the kind which some philosophers would call a sensation, and others would call a sense-datum. Whether all philosophers, when they talk of sensations, mean to include among them such objects as these, I do not know. Some, who have given a great deal of attention to the subject, and for whom I have a great respect, talk of sensations in such a way, that I cannot be sure what they are talking about at all or whether there are such things. But many, I think, undoubtedly do mean to include such subjects as these. No doubt, in general, when they call them sensations, they mean to attribute to them properties, which it seems to me extremely doubtful whether they possess. And perhaps even those who call them sense-data, may, in part, be attributing to them properties which it may be doubtful whether they possess. If we want to define a sensation or a sense-datum, in a manner which will leave it not open to doubt what sort of things we are talking of, and that there are such things, I do not know that we can do it better than by saying that sense-data are the sort of things, about which such judgments as these always seem to be made—the sort of things which seem to be the real or ultimate subjects of all such judgments. Such a way of defining how the term "sense-datum" is used, may not seem very satisfactory; but I am inclined to think it may be as satisfactory as any which can be found. And it is certainly calculated to obviate some misunderstandings which may arise; since everybody can see, I think, what the thing is which I am describing as the thing about which he is making his judgment, when he judges "That is an inkstand," and that there is such a thing, even if he does not agree that this description applies to it.
I can, in fact, imagine that some of those who would call this thing a sensation would deny that my judgment is about it at all. It would sometimes be spoken of as the sensation which mediates my perception of this inkstand in this instance. And I can imagine that some of those who would so speak of it might be inclined to say that when I judge "This is an inkstand," my judgment is about this inkstand which I perceive, and not, in any sense at all, about the sensation which mediates my perception of it. They may perhaps imagine that the sensation mediates my perception of the inkstand only in the sense that it brings the inkstand before my mind in such a way that, once it is before my mind, I can make a judgment about it, which is not a judgment about the mediating sensation at all; and that such a judgment is the one I am actually expressing when I say "This is an inkstand." Such a view, if it is held, seems to me to be quite certainly false, and is what I have intended to deny. And perhaps I can put most clearly the reason why it seems to me false, by saying that, if (which may be doubted) there is anything which is this inkstand, that thing is certainly not given to me independently of this sense-datum, in such a sense that I can possibly make a judgment about it which is not a judgment about this sense-datum. I am not, of course, denying that I do perceive this inkstand, and that my judgment is, in a sense, a judgment about it. Both these things seem to me to be quite obviously true. I am only maintaining that my judgment is also, in another sense, a judgment about this sense-datum which mediates my perception of the inkstand. Those who say that this sense-datum does mediate my perception of the inkstand, would, of course, admit that my perception of the inkstand is, in a sense, dependent upon the sense-datum; that it is dependent is implied in the mere statement that it is mediated by it. But it might be maintained that it is dependent on it only in the sense in which, when the idea of one object is called up in my mind, through association, by the idea of another, the idea which is called up is dependent on the idea which calls it up. What I wish to maintain, and what seems to me to be quite certainly true, is that my perception of this inkstand is dependent on this sense-datum, in a quite different and far more intimate sense than this. It is dependent on it in the sense that, if there is anything which is this inkstand, then, in perceiving that thing, I am knowing it only as the thing which stands in a certain relation to this sense-datum. When the idea of one object is called up in my mind by the idea of another, I do not know the second object only as the thing which has a certain relation to the first: on the contrary, I can make a judgment about the second object, which is not a judgment about the first. And similarly in the case of two sense-data which are presented to me simultaneously, I do not know the one only as a thing which has a certain relation to the other. But in the case of this sense-datum and this inkstand the case seems to me to be plainly quite different. If there be a thing which is this inkstand at all, it is certainly only known to me as the thing which stands in a certain relation to this sense-datum. It is not given to me, in the sense in which this sense-datum is given. If there be such a thing at all, it is quite certainly only known to me by description, in the sense in which Mr. Russell uses that phrase; and the description by which it is known is that of being the thing which stands to this sense-datum in a certain relation. That is to say, when I make such a judgment as "This inkstand is a good big one"; what I am really judging is: "There is a thing which stands to this in a certain relation, and which is an inkstand, and that thing is a good big one"—where "this" stands for this presented object. I am referring to or identifying the thing which is this inkstand, if there be such a thing at all, only as the thing which stands to this sense-datum in a certain relation; and hence my judgment, though in one sense it may be said to be a judgment about the inkstand, is quite certainly also, in another sense, a judgment about this sense-datum. This seems to me so clear, that I wonder how anyone can deny it; and perhaps nobody would. But I cannot help thinking that it is not clear to everybody; partly because, so far as I can make out, nobody before Mr. Russell had pointed out the extreme difference there is between a judgment about a thing known only by description to the individual who makes the judgment, and a judgment about a thing not known to him only in this way; and partly because so many people seem still utterly to have failed to understand what the distinction is which he expresses in this way. I will try to make the point clear, in a slightly different way. Suppose I am seeing two coins, lying side by side, and am not perceiving them in any other way except by sight. It will be plain to everybody, I think, that, when I identify the one as "This one" and the other as "That one," I identify them only by reference to the two visual presented objects, which correspond respectively to the one and to the other. But what may not, I think, be realised, is that the sense in which I identify them by reference to the corresponding sense-data, is one which involves that every judgment which I make about the one is a judgment about the sense-datum which corresponds to it, and every judgment I make about the other, a judgment about the sense-datum which corresponds to it: I simply cannot make a judgment about either, which is not a judgment about the corresponding sense-datum. But if the two coins were given to me, in the sense in which the two sense-data are, this would certainly not be the case. I can identify and distinguish the two sense-data directly, this as this one, and that as that one: I do not need to identify either as the thing which has this relation to this other thing. But I certainly cannot thus directly identify the two coins. I have not four things presented to me (1) this sense-datum, (2) that sense-datum, (3) this coin, and (4) that coin, but two only—this sense-datum and that sense-datum. When, therefore, I judge "This is a coin," my judgment is certainly a judgment about the one sense-datum, and when I judge "And that is also a coin," it is certainly a judgment about the other. Only, in spite of what my language might seem to imply, I am certainly not judging either of the one sense-datum that it is a whole coin, nor yet of the other that it is one.
This, then, seems to me fundamentally certain about judgments of this kind. Whenever we make such a judgment we can easily pick out an object (whether we call it a sensation or a sense-datum, or not), which is, in an easily intelligible sense, the object which is the real or ultimate subject of our judgment; and yet, in many cases at all events, what we are judging with regard to this object is certainly not that it is an object of the kind, for which the term which appears to express the predicate of our judgment is a name.
But if this be so, what is it that I am judging, in all such cases, about the presented object, which is the real or ultimate subject of my judgment? It is at this point that we come to questions which seem to me to be really uncertain and difficult to answer.